"Whoever catches up with a Rak'ah of the Subh prayer before the sun rises, then he has caught up with Subh, and whoever catches up with a Rak'ah of 'Asr prayer before the sun sets, then he has caught up with 'Asr." (Using translation from Nasāʾī 517)
أَنَّ رَسُولَ اللهِ ﷺ قَالَ مَنْ أَدْرَكَ رَكْعَةً مِنَ الصُّبْحِ قَبْلَ أَنْ تَطْلُعَ الشَّمْسُ فَقَدْ أَدْرَكَ ومَنْ أَدْرَكَ رَكْعَةً مِنَ الْعَصْرِ قَبْلَ أَنْ تَغْرُبَ الشَّمْسُ فَقَدْ أَدْرَكَ الْعَصْرَ